Xerographic fixing device

Claim 2

In a pressure heat roll image fixing apparatus of the type wherein a heated roll is moved into pressure contact against a coacting back up roll to form a fusing nip therebetween through which images bearing support sheets are drawn, the improvement comprising evaporator means positioned in thermal communication with said back up roll to remove heat energy from the surface of said roll, said evaporator means being wrapped in a blanket material having relatively high thermal conductivity and a relatively low coefficient of friction with respect to said roll surface, and means operatively connected to said evaporator means for discharging the heat energy removed from said roll surface into a receiver which is thermally isolated from said roll surface.

Claim 3

The apparatus of claim 1 wherein said evaporator removes heat energy from the fuser roll surface under isothermal conditions.

Claim 6

The method of claim 3, further including the step of returning the condensate of said working substance back into thermal communication with said fusing system.

Claim 7

The method of claim 4, further including the step of throttling the condensate prior to returning said condensate back into thermal communication with said fusing system.

Claim 8

Apparatus for reducing the surface temperature of a xerographic fuser roll to a predetermined temperature including a pair of parallel aligned evaporator units positioned in thermal communication with the fuser roll surface, said units being partially filled with a working fluid capable of evaporating at about the predetermined temperature, a pair of condenser units for receiving the evaporants of the working substance from said evaporator units, said condensers being located in a region thermally isolated from said fuser region, a vapor line connecting one of each evaporator units to one of each condenser units, and a liquid return line for returning condensate from each condenser unit to an evaporator unit opposite that from which said condenser receives evaporants.

Claim 9

Apparatus for reducing the surface temperature of a xerographic fuser roll to a predetermined temperature including a pair of parallel aligned evaporator units positioned in thermal communication with the fuser roll surface, said units being partially filled with a working fluid capable of evaporating at about the predetermined temperature, a pair of condenser units for receiving the evaporants of the working substance from said evaporator units, said condensers being located in a region thermally isolated from said fuser region, a vapor line connecting one of each evaporator units to one of each condenser units, and a liquid return line for returning condensate from each condenser unit to an evaporator unit opposite that from which said condenser receives evaporants.

Claim 10

The apparatus of claim 6, having further means to maintain the working fluids contained in each evaporator unit at substantially the same level.

Claim 11

The apparatus of claim 6, wherein each evaporator is located at a lower elevation than the condenser units whereby the evaporants and condensates of the working substance are caused to flow therebetween under natural flow conditions.

Claim 12

The apparatus of claim 6, wherein said evaporators are supported within a blanket having a relatively high thermal conductivity, said blanket being positioned in contact against at least a portion of said fuser roll surface.

Claim 13

The apparatus of claim 9, wherein said blanket has a low coefficient of friction in regard to said fuser roll surface.

Claim 14

The apparatus of claim 6, further including an expansion valve in each of the condensate return lines.

Claim 15

The apparatus of claim 6, having connecting means running between the liquid return lines for equalizing the amount of condensate carried in each of said lines.

Claim 16

The apparatus of claim 7, wherein said means to maintain the fluid level in each evaporator at substantially the same level includes a closed conduct between each evaporator, said conduct opening into each evaporator above the normal fluid level contained therein, and a wick element running through said conduct with both ends of said wick positioned below the fluid level of each evaporator unit.